Front fork and vehicle suspension structure

Abstract

A front fork (F) comprises a fork main body (1) having a vehicle body-side tube (2) and an axle-side tube (3), a damper cartridge (D) having a cylinder (10) and a rod (11) that enters and exits the cylinder (10), an axle bracket (4) that closes the lower end of the axle-side tube (3), and a connecting member (20) that connects one end of the damper cartridge (D) to the axle bracket (4), wherein: the axle bracket (4) has a lid portion (41) that closes the lower end of the axle-side tube (3), and an axle connection portion (43) provided to the side of the lid portion (41); a connecting member insertion hole (44) is provided penetrating through the lid portion (41) along the axial direction of the fork body (1) to allow insertion of the connecting member (20) that connects the damper cartridge (D); and an axle attachment hole (45) that partially intersects the connecting member insertion hole (44) is provided in the axle connection portion (43) to allow insertion of an axle (30).

Description

Front fork and vehicle suspension structure

[0001] The present invention relates to a front fork and a vehicle suspension structure.

[0002] A front fork is used in a straddle-type vehicle, supports a front steering wheel of the straddle-type vehicle, exerts a damping force when expanding and contracting, and suppresses vibration of a vehicle body. Such a front fork includes: a vehicle body-side tube connected to a vehicle body; an axle-side tube movably inserted into the vehicle body-side tube and connected to an axle to which the steering wheel is attached; an axle bracket that closes a lower end of the axle-side tube and holds the axle; and a damper cartridge interposed between the vehicle body-side tube and the axle-side tube.

[0003] The damper cartridge includes a cylinder, a piston rod inserted into the cylinder, a piston connected to the piston rod and inserted into the cylinder to divide the interior of the cylinder into an extension chamber and a compression chamber, and a damping valve that provides resistance to the flow of hydraulic oil flowing between the extension chamber and the compression chamber during expansion and contraction operations. The damper cartridge generates a damping force when expanding and contracting in response to vibration input during traveling of the straddle-type vehicle, thereby suppressing vibration of the vehicle body.

[0004] In a front fork configured as described above, for example, as disclosed in JP2025-018020A, the axle bracket has a bottomed cylindrical shape, and a bottom portion that closes the lower end of the axle-side tube is provided with a hole penetrating the bottom portion. The damper cartridge is fastened to the axle bracket by screwing a screw member into the hole and screwing the piston rod of the damper cartridge to the screw member.

[0005] JP2025-018020A

[0006] The axle bracket in the front fork configured in this way is equipped with a C-shaped axle coupling section at its bottom to grip the axle of the steering wheel. The axle coupling section has a bolt insertion hole at one end in the circumferential direction that allows a bolt to be inserted, and a screw hole at the other end in the circumferential direction into which the bolt is screwed. The axle is gripped by using the bolt to pull both ends in the circumferential direction together and tighten the axle that is inserted inward.

[0007] The front fork, to which the axle is attached in this manner, is connected to the vehicle body via a bracket that is fixed to a steering shaft, which is rotatably mounted on the head pipe at the front of the vehicle body of a saddle-type vehicle.

[0008] The front fork not only functions as a suspension system that suspends the steering wheels from the vehicle body, but also transmits the driver's steering input to the steering wheels, causing them to turn. In off-road motorcycles such as motocross bikes, where off-road capability is expected primarily for riding on rough terrain, steering performance is prioritized and it is preferable to reduce the trail. One way to reduce the trail is to position the axle in front of the axis of the front fork. In conventional front forks 100, as shown in Figure 5, an axle connecting part 102 is provided in front of the bottom of the axle bracket 101, so that the axle 103 is positioned in front of the axis 104 of the front fork 100.

[0009] On the other hand, in road bike models where on-road riding performance is primarily expected, such as on tarmac, straight-line stability is prioritized, so it is better to have a larger trail. The axle connection is provided at the lower end of the bottom of the axle bracket, and the axle is aligned with the axis of the front fork to secure the trail.

[0010] In recent years, with the growing popularity of adventure bikes, often referred to as dual-purpose or crossover bikes that can handle both on-road and off-road riding with ease, there has been a demand for front forks that can achieve a trail suitable for adventure bikes.

[0011] The ideal trail length for an adventure bike is between that of an off-road bike and an on-road bike, in order to accommodate both off-road and on-road riding. Therefore, compared to an axle bracket for an off-road bike, the axle needs to be positioned closer to the axis of the front fork.

[0012] Furthermore, adventure bikes are often heavier than off-road bikes, and their axle diameters are also larger than those of off-road bikes.

[0013] Therefore, in order to make the front fork usable on adventure bikes, it is necessary to enlarge the axle connection section and bring the axle closer to the axis of the front fork. However, with conventional front forks, the axle connection section must be positioned to avoid the screw member housed in a hole that penetrates the bottom of the axle bracket axially, making it impossible to achieve the appropriate amount of trail for adventure bikes.

[0014] Therefore, the present invention aims to provide a front fork and vehicle suspension structure that enables a layout in which the axle is positioned near the axis of the front fork.

[0015] To achieve the above objectives, the front fork in the problem-solving means of the present invention comprises a fork body having a vehicle body side tube and an axle side tube that is axially movable relative to the vehicle body side tube, a damper cartridge housed in the fork body having a cylinder and a rod that moves in and out of the cylinder, an axle bracket attached to the lower end of the axle side tube and closing the lower end of the axle side tube, and a connecting member that connects one end of the damper cartridge to the axle bracket, the axle bracket having a cover portion that closes the lower end of the axle side tube and an axle connecting portion provided on the side of the cover portion and connectable to an axle, the cover portion is provided with a connecting member insertion hole that penetrates along the axial direction of the fork body and allows insertion of a connecting member that connects the damper cartridge, and the axle connecting portion is provided with an axle mounting hole that penetrates along the axial direction of the axle and allows insertion of an axle and partially intersects with the connecting member insertion hole.

[0016] With this front fork configuration, the axle mounting hole, which is provided in the axle connection section horizontally and into which the axle is inserted, partially intersects with the axle connection section into which the connecting member for connecting the damper cartridge is inserted. Therefore, even if the axle is enlarged, it is possible to achieve a layout in which the axis passing through the center of the axle is positioned close to the axis of the fork body.

[0017] Furthermore, the vehicle suspension structure may have a front fork and an axle inserted into an axle mounting hole, with the connecting member inserted into a connecting member insertion hole, and the axle having a recess that allows the connecting member to be inserted into the connecting member insertion hole. In a vehicle suspension structure configured in this way, even if a bolt screwed into the axle connection part falls out for some reason, the connecting member fits into the recess of the intersecting axle, thus preventing the axle from falling out of the axle mounting hole.

[0018] Figure 1 is a cross-sectional view of a front fork in one embodiment of the present invention. Figure 2 is a side view of the front portion of a saddle-type vehicle equipped with a vehicle suspension structure in one embodiment of the present invention. Figure 3 is a partially enlarged cross-sectional view of a front fork in one embodiment of the present invention. Figure 4 is a perspective view showing a connecting member and axle in a modified example of one embodiment of the present invention. Figure 5 is a cross-sectional view of a conventional front fork.

[0019] The present invention will be described below based on the embodiments shown in the figures. In this embodiment, the front fork F, as shown in Figures 1 to 3, comprises a fork body 1 having a vehicle body side tube 2 and an axle side tube 3 that is axially movable relative to the vehicle body side tube 2; a damper cartridge D housed in the fork body 1, having a cylinder 10 and a rod 11 that moves in and out of the cylinder 10; an axle bracket 4 attached to the outer circumference of the lower end of the axle side tube 3 to close the lower end of the axle side tube 3; and a connecting member 20 connecting one end of the damper cartridge D to the axle bracket 4. Furthermore, as shown in Figure 2, the front fork F is used interposed between the vehicle body B and the front wheel W of the saddle-type vehicle V, with the vehicle body side tube 2 connected to the vehicle body B of the saddle-type vehicle V, and the axle side tube 3 connected via the axle bracket 4 to the axle 30 to which the front wheel W of the saddle-type vehicle V is rotatably mounted.

[0020] In this embodiment, the front fork F is formed in a telescopic shape, in which an axle-side tube 3, positioned below the saddle-type vehicle V, is inserted axially into a body-side tube 2, positioned above the saddle-type vehicle V, and is used in a vehicle suspension structure A that suspends the front wheel W of the saddle-type vehicle V. It expands and contracts in accordance with the relative movement between the vehicle body B and the front wheel W. Furthermore, in this embodiment, the front fork F houses a damper cartridge D interposed between the body-side tube 2 and the axle-side tube 3, which generates damping force when the axle-side tube 3 moves axially relative to the body-side tube 2, and a suspension spring S interposed between the body-side tube 2 and the axle-side tube 3, which biases them to move apart. In this space, outside the damper cartridge D, hydraulic fluid (not shown) is stored.

[0021] The following describes the various parts of the front fork F in detail. The upper end of the vehicle-side tube 2 is closed by a head cap 5. A seal 9 is provided on the inner circumference of the lower end of the vehicle-side tube 2, which slides against the outer circumference of the axle-side tube 3, thus sealing the space between the vehicle-side tube 2 and the axle-side tube 3. The space between the lower end of the axle-side tube 3 and the axle bracket 4 is sealed by a seal case 6. Therefore, the inside of the fork body 1, formed by the vehicle-side tube 2 and the axle-side tube 3, is airtightly sealed. In this embodiment of the front fork F, the axle-side tube 3 is inserted into the vehicle-side tube 2, but conversely, the vehicle-side tube 2 may be made smaller in diameter and inserted into the axle-side tube 3.

[0022] The damper cartridge D, although not shown in detail, includes, for example, a cylinder 10 connected to a head cap 5 mounted on the upper end of the vehicle body tube 2, a cylindrical rod 11 connected to the axle bracket 4 by a cylindrical connecting member 20 and movably inserted into the cylinder 10, a piston 12 inserted into the cylinder 10 and connected to the rod 11 to divide the inside of the cylinder 10 into an extension chamber R1 and a compression chamber R2, an extension port 12a and a compression port 12b provided on the piston 12 that connect the extension chamber R1 and the compression chamber R2, and a component stacked above the piston 12 in Figure 1 that opens and closes the extension port 12a and controls the liquid passing through the extension port 12a. The device includes an extension leaf valve 13 that provides resistance to the flow, a pressure leaf valve 14 stacked below the piston 12 in Figure 1 which opens and closes the pressure port 12b and provides resistance to the flow of liquid passing through the pressure port 12b, a needle valve 15 having a bypass passage P that bypasses the extension port 12a and the pressure port 12b through the rod 11, a needle valve body 15b that is inserted into the rod 11 so as to be movable in the axial direction and is seatable on and off an annular valve seat 15a provided in the bypass passage P, and a control rod 16 that is inserted into the rod 11 so as to be movable in the axial direction, with one end abutting against the needle valve 15 and the other end protruding from the lower end of the rod 11.

[0023] The lower end of the cylinder 10 is closed by an annular rod guide 18 through which the rod 11 is inserted. The rod guide 18 guides the axial movement of the rod 11 relative to the cylinder 10.

[0024] When the damper cartridge D extends and the piston 12 moves downward relative to the cylinder 10 in Figure 1, the extension leaf valve 13 and needle valve 15 provide resistance to the flow of liquid moving from the contracting extension chamber R1 to the expanding compression chamber R2, thereby generating an extension damping force that hinders the extension operation.

[0025] Furthermore, when the damper cartridge D exhibits a contraction operation and the piston 12 moves upward relative to the cylinder 10 in Figure 1, the pressure-side leaf valve 14 and needle valve 15 provide resistance to the flow of liquid moving from the contracted pressure-side chamber R2 to the expanded extension-side chamber R1, thereby generating a pressure-side damping force that hinders the contraction operation.

[0026] Furthermore, in the damper cartridge D, the damping force on the extension side and the damping force on the compression side can be adjusted by adjusting the opening area of ​​the needle valve 15, thereby adjusting the resistance that the needle valve 15 imposes on the flow of liquid passing through the bypass path P.

[0027] Furthermore, the damper cartridge D has an air chamber (not shown) inside the cylinder 10, and compensates for the volume of the rod 11 moving in and out of the cylinder 10 by absorbing the volume of the rod 11 moving in and out of the cylinder 10 when it extends and retracts by expanding and contracting the air chamber. Alternatively, the space inside the fork body 1 outside the damper cartridge D may be used as a reservoir where liquid is stored, and the volume of the rod 11 moving in and out of the cylinder 10 may be compensated for by exchanging liquid between the inside of the cylinder 10 and the reservoir.

[0028] Furthermore, the configuration of the damper cartridge D is not limited to the structure described above, and the damper cartridge D may exert damping force only through extension or contraction. In addition, although the cylinder 10 of the damper cartridge D is connected to the vehicle body side tube 2 and the rod 11 is connected to the axle side tube 3, it may also be installed upside down in the figure, with the cylinder 10 connected to the axle side tube 3 and the rod 11 connected to the vehicle body side tube 2.

[0029] Furthermore, the suspension spring S is interposed between the suspension spring receiver 17 mounted on the outer circumference of the cylinder 10 and the seal case 6 placed on the axle bracket 4, biasing the vehicle body side tube 2 and the axle side tube 3 in a direction that separates them from each other, and constantly biasing the fork body 1 in the extension direction. Therefore, when the front fork F is installed between the vehicle body B and the front wheel W, the suspension spring S generates elastic force and elastically supports the vehicle body B. In the illustration, the suspension spring S is shown as a coil spring, but it may also be an air spring formed by sealing pressurized gas inside the fork body 1 and outside the damper cartridge D.

[0030] Next, as shown in Figure 3, a threaded portion 3b is provided on the outer circumference of the lower end of the axle-side tube 3, and as described above, an axle bracket 4 that holds the axle 30 of the front wheel W of the saddle-type vehicle V is attached, and the opening at the lower end 3a of the axle-side tube 3 is closed by the axle bracket 4.

[0031] As shown in Figure 3, the axle bracket 4 includes a cover portion 41 that closes the lower end 3a of the axle-side tube 3, a cylindrical portion 42 that rises from the outer circumference of the cover portion 41, covers the outer circumference of the lower end of the axle-side tube 3, and is screw-connected to the axle-side tube 3, an axle connecting portion 43 provided on the side of the cover portion 41 that connects to the axle 30 on which the front wheel W is mounted, a connecting member insertion hole 44 that penetrates the cover portion 41 along the axial direction of the fork body 1 and allows the insertion of a connecting member 20 that connects to the damper cartridge D, and an axle mounting hole 45 provided horizontally in the axle connecting portion 43 that partially intersects with the connecting member insertion hole 44.

[0032] In this embodiment of the front fork F, the cover portion 41 is cylindrical in shape, and the cover portion 41 is provided with a connecting member insertion hole 44 that opens from the lower end along the axial direction of the fork body 1 and leads to the upper end. The connecting member insertion hole 44 has a larger inner diameter on the lower side than on the upper side, and comprises a larger diameter portion 44a on the lower side and a smaller diameter portion 44b on the upper side, as well as a threaded portion 44c from the upper end to the middle of the smaller diameter portion 44b to which the connecting member 20 is screwed.

[0033] The cylindrical portion 42 rises upward from the outer circumference of the lid portion 41 and has a threaded portion 42a on its inner circumference to enable screw connection to the threaded portion 3b provided on the outer circumference of the axle-side tube 3.

[0034] As described above, the axle bracket 4 is a bottomed cylindrical shape comprising a lid portion 41 and a cylindrical portion 42. When the cylindrical portion 42 is fastened to the axle-side tube 3 by screw connection, the lid portion 41 faces the opening at the lower end 3a of the axle-side tube 3 and closes the lower end 3a. When the axle bracket 4 is fastened to the axle-side tube 3 by screw connection, the seal case 6 is sandwiched between the lower end 3a of the axle-side tube 3 and the lid portion 41.

[0035] The seal case 6 comprises an annular base 6a that fits onto the inner circumference of the lower end 3a of the axle-side tube 3, a flange 6b that protrudes radially from the outer circumference of the lower end of the base 6a and is sandwiched between the lower end 3a of the axle-side tube 3 and the lid 41, a cylindrical lock case 6c that rises from the inner circumference of the base 6a, and annular grooves 6d and 6e provided on the lower end and outer circumference of the base 6a. A seal ring 7 that is in close contact with the upper end of the lid 41 in Figure 3 is housed in the annular groove 6d of the seal case 6, and a seal ring 8 that is in close contact with the inner circumference of the axle-side tube 3 is housed in the annular groove 6e of the seal case 6, and the space between the axle-side tube 3 and the axle bracket 4 is sealed by the seal case 6 with these seal rings 7 and 8 installed. The lock case 6c of the seal case 6 allows the rod guide 18, which is attached to the lower end of the cylinder 10, to enter inward when the damper cartridge D is fully contracted. Furthermore, an annular lock piece 19 is attached to the outer circumference of the lower end of the rod guide 18 in Figure 1. When the lock piece 19 enters the lock case 6c, the chamber inside the lock case 6c is closed by the lock piece 19 and the rod guide 18, and the chamber is pressurized, exhibiting a hydraulic lock function that prevents the front fork F from contracting.

[0036] Returning to the previous point, the axle connecting portion 43 protrudes forward from the right side of the cover portion 41, which is on the front side of the vehicle in Figure 3. The axle connecting portion 43 is provided with an axle mounting hole 45 that penetrates the axle connecting portion 43 horizontally, and a split 43a that opens from the front end, which is the right end in Figure 3, and leads to the axle mounting hole 45. The axle connecting portion 43 is provided with a pair of arms 43b and 43c that form the axle mounting hole 45 on both sides of the split 43a. In Figure 3, the upper arm 43b has a screw hole 43d that opens from the surface facing the split 43a and penetrates the arm 43b diagonally upward, and the lower arm 43c has a bolt insertion hole 43e that opens from the surface facing the split 43a and penetrates the arm 43c diagonally downward, and is directly opposite the screw hole 43d.

[0037] Therefore, when the axle 30 is inserted into the axle mounting hole 45 formed in the axle connecting portion 43, and the bolt 50 is inserted into the bolt insertion hole 43e and the screw hole 43d, and the bolt 50 is screwed into the screw hole 43d, the tips of the arms 43b and 43c are brought closer together, narrowing the split 43a and reducing the diameter of the axle mounting hole 45, so that the axle 30 is tightly fastened and firmly fixed to the axle connecting portion 43.

[0038] The connecting member insertion hole 44 provided in the lid portion 41 is formed along the axial direction of the lid portion 41, and the axle mounting hole 45 is provided through the axle connecting portion 43, which is located in front of the side of the lid portion 41 and protrudes forward from the right side in Figure 3, along the axis X of the axle 30 and in a transverse direction that crosses the axis Y of the fork body 1 and penetrates the plane of the paper in Figure 3. The connecting member insertion hole 44 and the axle mounting hole 45 are formed with parts of them intersecting each other. Specifically, the axle mounting hole 45 intersects and communicates with the connecting member insertion hole 44 in the middle of the large diameter portion 44a. Because parts of the connecting member insertion hole 44 and the axle mounting hole 45 intersect in this way, when the axle 30 is inserted into the axle mounting hole 45, a part of the side of the axle 30 enters the connecting member insertion hole 44.

[0039] The connecting member 20 comprises a cylindrical adjuster case 21 and an adjuster 22 housed within the adjuster case 21. The adjuster case 21 is cylindrical, with a smaller outer diameter on the upper side in Figure 3, and has an outer small diameter portion 21a with a threaded portion on its outer circumference, an outer large diameter portion 21b connected to the lower end of the outer small diameter portion 21a, and an annular recess 21c provided in the middle of the axial direction of the outer large diameter portion 21b. It also has an inner threaded portion 21d into which the rod 11 is screw-connected, a control rod insertion portion 21e connected to the lower end of the inner threaded portion 21d that allows the insertion of the control rod 16 and has an inner diameter smaller than the inner threaded portion 21d, and an adjuster housing portion 21f connected to the lower end of the control rod insertion portion 21e that houses the adjuster 22. Furthermore, the adjuster case 21 is equipped with an annular tool engagement portion 21g that protrudes from its lower end, enabling gripping by a tool.

[0040] The outer diameter of the small-diameter portion 21a is such that it can be inserted into the small-diameter portion 44b of the connecting member insertion hole 44. The adjuster case 21 is fixed to the axle bracket 4 by screwing the outer diameter of the small-diameter portion 21a to the screw portion 44c provided on the inner circumference of the connecting member insertion hole 44. The outer diameter of the outer diameter portion 21b of the adjuster case 21 is larger than the small-diameter portion 44b of the connecting member insertion hole 44 of the axle bracket 4, and is such that it can be inserted into the large-diameter portion 44a. The outer diameter of the large-diameter portion 21b of the adjuster case 21 is housed within the large-diameter portion 44a of the connecting member insertion hole 44.

[0041] Furthermore, the inner circumferential threaded portion 21d of the adjuster case 21 is screw-connected to the threaded portion 11a provided on the outer circumference of the lower end of the rod 11 in Figure 3 of the damper cartridge D. Thus, in the front fork F of this embodiment, one end of the damper cartridge D is the rod 11, and the rod 11 is connected to the axle bracket 4 via the connecting member 20. Therefore, the rod 11 is connected to the axle-side tube 3 via the connecting member 20 and the axle bracket 4. A nut 25, whose lower end abuts against the upper end of the adjuster case 21, is screw-connected to the threaded portion 11a of the rod 11, and the rod 11 and the adjuster case 21 are prevented from loosening by tightening the nut 25. When screw-connecting the adjuster case 21 to the axle bracket 4, the adjuster case 21 can be easily tightened to the axle bracket 4 by gripping the tool engagement portion 21g provided on the lower end of the adjuster case 21 in Figure 3 with a tool and using the tool.

[0042] When the adjuster case 21 is connected to the axle bracket 4 in this manner, the annular recess 21c provided on the outer circumference of the large-diameter outer circumference portion 21b of the adjuster case 21 faces radially a part of the axle mounting hole 45 that opens into the connecting member insertion hole 44.

[0043] A depth H of the recess 21c in the adjuster case 21 is formed deep enough to avoid interfering with the columnar axle 30 inserted into the axle mounting hole 45, and does not hinder the insertion of the axle 30 into the axle mounting hole 45. As described above, the recess 21c is provided so as not to overlap the axle mounting hole 45 when viewed from the direction of an axis X of the axle 30, and to avoid the axle mounting hole 45.

[0044] The adjuster 22 accommodated in the adjuster accommodation portion 21f of the adjuster case 21 is columnar, and includes a body portion 22a accommodated in the adjuster accommodation portion 21f, a head portion 22b that protrudes from the upper end of the body portion 22a in FIG. 3 and is screwed onto a screw portion formed on an inner circumference of a lower end portion of a control rod insertion portion 21e in FIG. 3, and an operation portion 22c that protrudes downward from the lower end of the body portion 22a in FIG. 3, which is a rear end of the body portion 22a, and has a groove allowing insertion of a tool such as a screwdriver.

[0045] When the operation portion 22c is rotated using a tool, the head portion 22b also rotates, and the entire adjuster 22 advances and retreats within the adjuster case 21. Since the head portion 22b is in contact with the lower end of the control rod 16 in FIG. 3, when the adjuster 22 is rotated relative to the adjuster case 21 fixed to an axle bracket 4 and moved in the axial direction relative to the adjuster case 21, the control rod 16 moves axially inside the rod 11 together with the adjuster 22, whereby the position of a needle valve body 15b of a needle valve 15 relative to an annular valve seat 15a can be adjusted.

[0046] An annular stopper 23 is mounted in a tool engagement portion 21g of the adjuster case 21, and the stopper 23 prevents the adjuster 22 from coming off the adjuster case 21. A plurality of unillustrated grooves are formed along the axial direction on an inner circumferential surface of an upper end of the stopper 23 in FIG. 3. A pair of unlabeled balls and a spring inserted between the balls are accommodated in a hole 22d of the body portion 22a of the adjuster 22, the spring biasing each ball in a direction to come out of the hole 22d, so that rotation of the adjuster 22 can be restricted at a position where the balls fit into the grooves.

[0047] The front fork F configured as described above comprises a fork body 1 having a vehicle body side tube 2 and an axle side tube 3 that is axially movable relative to the vehicle body side tube 2; a damper cartridge D housed within the fork body 1 and having a cylinder 10 and a rod 11 that moves in and out of the cylinder 10; an axle bracket 4 attached to the lower end of the axle side tube 3 and closing the lower end of the axle side tube 3; and a connecting member 2 connecting one end of the damper cartridge D to the axle bracket 4. The axle bracket 4 comprises a cover portion 41 that closes the lower end of the axle-side tube 3, and an axle connecting portion 43 provided to the side of the cover portion 41 and connectable to the axle 30. The cover portion 41 is provided with a connecting member insertion hole 44 that penetrates along the axial direction of the fork body 1 and allows the insertion of a connecting member 20 that connects the damper cartridge D. The axle connecting portion 43 is provided with an axle mounting hole 45 that penetrates along the axial direction of the axle 30 and allows the insertion of the axle 30, and partially intersects with the connecting member insertion hole 44.

[0048] According to the front fork F configured as described above, the axle mounting hole 45, which is provided in the axle connecting portion 43 in the horizontal direction and into which the axle 30 is inserted, partially intersects the connecting member insertion hole 44 into which the connecting member 20 for connecting the damper cartridge D is inserted. Therefore, the distance L1 between the axis X passing through the center of the axle 30 and the axis Y of the fork body 1 can be shortened, allowing the axis X passing through the center of the axle 30 to be disposed in the vicinity of the axis Y of the fork body 1. In contrast, in the conventional front fork 100, as shown in FIG. 5, the axle 103 is disposed at a position avoiding the hole 101a in the bottom of the axle bracket 101. It will be understood that when the axle 103 increases in size, the distance L2 between the axis 105 of the axle 103 and the axis 104 of the front fork 100 becomes longer than the distance L1 in the front fork F of the present embodiment. As described above, according to the front fork F of the present embodiment, while the damper cartridge D is connected to the axle bracket 4 via the connecting member 20, a layout in which the axis X passing through the center of the axle 30 is disposed in the vicinity of the axis Y of the fork body 1 can be achieved even when the axle 30 increases in size. As described above, in the front fork F of the present embodiment, a layout in which the axis X passing through the center of the axle 30 is disposed in the vicinity of the axis Y of the fork body 1 can be achieved even when the axle 30 increases in size. Compared with the conventional front fork 100, the trail amount can be reduced and set to be appropriate for an adventure bike, so the front fork is optimal for use in an adventure bike.

[0049] In this embodiment, the front fork F connects the rod 11 in the damper cartridge D to the axle bracket 4 using a connecting member 20. However, the cylinder 10 may also be connected to the axle bracket 4 as one end of the damper cartridge D using a connecting member. When connecting the cylinder 10 to the axle bracket 4, for example, a cap that closes the cylinder 10 may be provided, a screw hole may be provided in the cap, a bolt may be inserted as a connecting member through hole 44, and the bolt may be screwed into the cap. Furthermore, if the front fork F includes a reservoir having a liquid chamber and an air chamber within the cylinder 10, a valve case housed within the reservoir and held by a cylindrical center rod fixed to the cylinder 10 to partition the pressure chamber and the liquid chamber, a discharge port and an intake port provided in the valve case that connect the pressure chamber and the liquid chamber, a pressure leaf valve stacked on the valve case to open and close the discharge port, an extension check valve stacked on the valve case to open and close the intake port, a pressure bypass path provided in the center rod that connects the pressure chamber and the liquid chamber by bypassing the discharge port, a needle valve provided in the middle of the pressure bypass path, and a control rod for adjusting the position of the needle valve, the cylinder 10 may be connected to the axle bracket 4 by connecting the center rod to the adjuster case 21 of the connecting member 20 instead of the rod 11, and the position of the needle valve may be adjusted via the control rod by the adjuster 22.

[0050] Furthermore, in the front fork F of this embodiment, the damper cartridge D has a control rod 16 for adjusting the damping force, and the connecting member 20 includes a cylindrical adjuster case 21 that is screw-connected to one end of the damper cartridge D and screw-connected to a connecting member insertion hole 44 in the axle bracket 4 into which one end of the control rod 16 is inserted, and an adjuster 22 that abuts against the control rod 16 and is screw-connected inside the adjuster case 21, and can move the control rod 16 forward and backward by rotational operation.

[0051] With the front fork F configured in this way, it is possible to achieve a layout in which the axis X passing through the center of the axle 30 is positioned near the axis Y of the fork body 1, while also allowing adjustment of the damping force of the damper cartridge D.

[0052] Furthermore, in the front fork F of this embodiment, the connecting member 20 is provided with a recess 21c on its outer circumference that avoids interference with the axle 30, at a position facing the axle mounting hole 45. With the front fork F configured in this way, even if the connecting member 20 is housed in the connecting member insertion hole 44, it does not interfere with the axle 30 inserted into the axle mounting hole 45. Therefore, there is no need to install the axle mounting hole 45 in a position that avoids the connecting member 20, and the axle mounting hole 45 can be installed to the side of the connecting member 20. As a result, the overall length of the cover portion 41 of the axle bracket 4 does not increase, and the length of the portion that does not contribute to the stroke of the front fork F does not become excessive. Thus, with the front fork F of this embodiment, a layout is achieved in which the axis X passing through the center of the axle 30 is positioned near the axis Y of the fork body 1, while not impairing vehicle mountability and ensuring sufficient stroke length. Furthermore, with the front fork F of this embodiment, even if the connecting member 20 loosens and tries to come out of the axle bracket 4, the axle 30 fits into the recess 21c, so there is no need to worry about the connecting member 20 falling off the axle bracket 4.

[0053] Furthermore, if the connecting member 20 includes an adjuster case 21 and an adjuster 22, and the connecting member 20 has an adjuster function for adjusting the damping force of the damper cartridge D, the outer diameter of the connecting member 20 tends to be large. Therefore, by providing the recess 21c as described above, the axle 30 can be positioned close to the axis Y of the front fork F while realizing the damping force adjuster function of the damper cartridge D, and the stroke length of the front fork F can also be secured, and the adjuster case 21 and adjuster 22 can be prevented from falling off. Furthermore, if the damper cartridge D is not equipped with a valve for adjusting the damping force, the connecting member 20 does not need to have an adjuster, and may be made of a bolt or the like that can connect the damper cartridge D to the axle bracket 4. However, if the bolt as the connecting member has a recess on its side to avoid the axle mounting hole 45, it is possible to connect the damper cartridge D to the axle bracket 4 while simultaneously realizing a layout in which the axis X passing through the center of the axle 30 is positioned near the axis Y of the fork body 1, even if the axle 30 is enlarged. This does not impair the ease of mounting on the vehicle, ensures sufficient stroke length, and prevents the connecting member 20 from falling off.

[0054] Furthermore, if the vehicle suspension structure A of this embodiment is configured to have a front fork F and an axle 30, as shown in Figure 4, the connecting member 20 is inserted into the connecting member insertion hole 44, and the axle 30 inserted into the axle mounting hole 45 may have a recess 30a that allows the connecting member 20 to be inserted into the connecting member insertion hole 44. In the vehicle suspension structure A configured in this way, even if a bolt 50 that is screw-connected to the axle connecting portion 43 falls out for some reason, the connecting member 20 fits into the recess 30a of the intersecting axle 30, thus preventing the axle 30 from falling out of the axle mounting hole 45.

[0055] Although preferred embodiments of the present invention have been described in detail above, modifications, alterations, and changes are permitted as long as they do not deviate from the scope of the claims.

[0056] 1...Fork body, 2...Vehicle side tube, 3...Vehicle side tube, 4...Axle bracket, 10...Cylinder, 11...Rod, 16...Control rod, 20...Connecting member, 21...Adjuster case, 21c...Recess in connecting member, 22...Adjuster, 30...Axle, 30a...Recess in axle, 41...Cover, 43...Axle connecting part, 44...Connecting member insertion hole, 45...Axle mounting hole, A...Vehicle suspension structure, D...Damper cartridge, X...Axle of axle, Y...Axle of front fork

Claims

1. A front fork comprising: a fork body having a body-side tube and an axle-side tube that is axially movable relative to the body-side tube; a damper cartridge housed within the fork body having a cylinder and a rod that moves in and out of the cylinder; an axle bracket attached to the lower end of the axle-side tube and closing the lower end of the axle-side tube; and a connecting member connecting one end of the damper cartridge to the axle bracket, wherein the axle bracket has a cover portion that closes the lower end of the axle-side tube, and an axle connecting portion provided to the side of the cover portion and connectable to an axle in a saddle-type vehicle, the cover portion is provided with a connecting member insertion hole that penetrates along the axial direction of the fork body and allows insertion of a connecting member that connects the damper cartridge, and the axle connecting portion is provided with an axle mounting hole that penetrates along the axis of the axle and allows insertion of the axle, and partially intersects with the connecting member insertion hole.

2. A front fork according to claim 1, wherein the damper cartridge has a control rod for adjusting damping force, and the connecting member has a cylindrical adjuster case that is screw-connected to one end of the damper cartridge and screw-connected to a connecting member insertion hole in the axle bracket into which one end of the control rod is inserted, and an adjuster that abuts against the control rod and is screw-connected to the adjuster case, and can move the control rod forward and backward by rotation.

3. A front fork according to claim 1, wherein the connecting member has a recess on its outer circumference at a position opposite to the axle mounting hole to avoid interference with the axle.

4. A vehicle suspension structure having a front fork as described in claim 1, comprising an axle inserted into the axle mounting hole, wherein the connecting member is inserted into the connecting member insertion hole, and the axle has a recess that allows the connecting member to be inserted into the connecting member insertion hole.

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